When I was first
building this pump, it took a while before I understood how these things work.
For those of you that aren't familiar with these type pumps, my explanation
below will hopefully help shorten this time for others.

Items are color coded to help
identify them.

As Steam
enters the pump, it travels to the Reversing Valve which is the vertical object (green) in the lower diagram.
The Reversing Valve,
when in its upward position, routes the Steam
to the back side of the Shuttle Valve Sleeve
which can be seen on the top diagram.

<<<
Steam In

Once the Steam
enters the back of the Shuttle
Valve Sleeve, it forces the
Shuttle Valve
to the other side (front). The
Steam
input is also routed directly to the
Shuttle Valve Sleeve,
bypassing the
Reversing Valve.
With the Shuttle Valve
in this position, the steam passages are open to the
Top-Right/Bottom-Left cylinders.

Remember, the steam section is not
cross-compounded, thus direct steam to both pistons.

As the Steam enters the
Top-Right/Bottom-Left cylinders, it pushes the steam pistons to the opposite ends.
The Exhaust
is routed through the Top-Left/Bottom-Right passages. The Exhaust
then goes to the Shuttle Valve Sleeve
where the Shuttle Valve
is already positioned to route the Exhaust
out.

Once the steam pistons reach the opposite
ends, the rightmost Piston Rod "pulls" down the Reversing Valve Rod/Piston.
This shuts off the Steam from the
back of the Shuttle Valve Sleeve
and routes Steam
to the front .

As the Steam enters the
front of the Shuttle Valve Sleeve,
it pushes the Shuttle Valve
towards the back. This routes the Steam
to the Top-Left/Bottom-Right cylinders.

With the Shuttle Valve
in the back position, the Top-Right/Bottom-Left cylinders are routed to the Exhaust.

Once the right Steam Piston reaches
the top, The Piston Rod pushes the Reversing Valve Rod/Piston
upwards and the cycle repeats.